ESTIMATION OF EFFECTIVE ION TEMPERATURES IN A QUADRUPOLE ION-TRAP

A modified Finnigan LCQ quadrupole ion trap has been used;ro determine the equilibrium constant of the complexation reaction of thiophenolat e with 2,2,2-trifluoroethanol. The process is particularly useful as a thermometer reaction because it has an exceptionally large temperatur e dependence. Using Literature values for the thermochemistry, an effe ctive ion temperature of 310 +/- 20 K is indicated for the ion trap. T his value is much lower than some earlier estimates for ion traps, but is consistent with a recent theoretical analysis and some previous in terpretations of experimental data. The results suggest that quadrupol e ion traps are suitable for studying gas phase reactions under nearly thermal conditions. (C) 1998 American Society for Mass Spectrometry.